Chemical vapor deposition (hereinafter "CVD") is defined as the formation of a non-volatile solid layer or film on a substrate by the reaction of vapor phase reactants that contain desired components. The vapors are introduced into a reactor vessel or chamber, and decompose and/or react at a heated surface on a wafer to form the desired layer. CVD is but one process of forming relatively thin layers on semiconductor wafers, such as layers of elemental metals or compounds. It is a favored layer formation process primarily because of its ability to provide highly conformal layers even within deep contacts and other openings.
For example, a compound, typically a heat decomposable volatile compound (also known as a precursor), is delivered to a substrate surface in the vapor phase. The precursor is contacted with a surface which has been heated to a temperature above the decomposition temperature of the precursor. A coating or layer forms on the surface. The layer generally contains a metal, metalloid, alloy, or mixtures thereof, depending upon the type of precursor and deposition conditions employed.
Precursors typically utilized in CVD are generally organometallic compounds, wherein a hydrocarbon portion of the precursor functions as the carrier for the metal or metalloid portion of the precursor during vaporization of the liquid precursor. For microelectronic applications, it is often desirable to deposit layers having high conductivity, which generally means that the layers should contain minimal carbon and oxygen contaminants. However, one problem of a CVD deposited layer formed from an organometallic precursor is incorporation of residual carbon from the hydrocarbon portion of the precursor and oxygen that may be present in the atmosphere during deposition. For example, oxygen incorporation into the layer before or after deposition generally results in higher resistivity. Further, it is also believed that organic incorporation (such as pure carbon or hydrocarbon) into the resultant layer reduces density and conductivity. A low density layer can subsequently lead to oxygen incorporation into the layer when it is exposed to ambient air.
Conductive layers formed by CVD processing can be used in the fabrication of various integrated circuits. For example, capacitors are the basic energy storage components in storage cells of memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and even in ferroelectric memory (FE) devices. As memory devices become more dense, it is necessary to decrease the size of circuit components. One way to retain storage capacity of memory devices and decrease its size is to increase the dielectric constant of the dielectric layer of the capacitor component. Such components typically consist of two conductive electrodes insulated from each other by a dielectric material. In order to retain storage capacity and to decrease the size of memory devices, materials having a relatively high dielectric constant can be used as the dielectric layer of a storage cell. Materials having relatively high dielectric constants are generally formed on a device surface as thin layers. Generally, high quality thin layers of metals and conductive metal oxides, nitrides, and silicides, are used as electrode materials for storage cell capacitors. To be effective electrodes, low resistivity is desired. Therefore, layers having low carbon and/or oxygen content are desired. Further, various applications also require such low resistivity conductive layers, e.g., contacts, interconnects, etc. In addition, the presence of carbon in an electrode layer may "poison" the dielectric layer thus, reducing the effectiveness of the capacitor.